1. Technical Field
The disclosure relates to an amplifier.
2. Description of Related Art
Silicon process techniques such as complementary metal-oxide semiconductor (CMOS) and SiGe have been widely and successfully used in wireless communication electronic circuits. Besides cost and size are considered, a main characteristic of the silicon process technique that various digital and analogic circuits can be integrated in a same process, so as to achieve a purpose of system-on-chip (SoC). However, to achieve a strict device specification for most of the communication systems, in a radio frequency (RF) circuit, besides the RF transceiver is implemented by the CMOS process, key components (for example, a power amplifier and a transceiver switch) of the front end RF circuit are all fabricated by a GaAs process with relatively high cost and better features due to a relatively great loss of the silicon substrate.
Compared to a conventional power amplifier of the GaAs process, disadvantages of a conventional power amplifier of the silicon process include low breakdown voltage, high loss of the silicon substrate and none backside via structure. The low breakdown voltage leads to a fact that the conventional power amplifier has to plan a lower drain bias and a lower alternating current (AC) voltage of an output terminal thereof, so that an optimal impedance of the output terminal of the power amplifier is greatly reduced. Therefore, implementation of impedance matching of the output terminal can lead to a relatively great loss especially on the substrate with higher silicon process loss. Therefore, the power amplifier known to a person of skill in the art implemented by the silicon process has lower efficiency, and remained energy is converted into heat and accumulated in the substrate. The accumulated heat can further influence a characteristic of the conventional power amplifier, such as a gain, an output power, etc.
Moreover, none backside via structure is provided during the CMOS process, so that in case of signal grounding of the amplifier of a common source structure, a bond wire has to be used to connect a printed circuit board or a package outside the chip, which may prolong the signal grounding path, and a parasitic inductance effect can severely influence the efficiency of the power amplifier. To resolve the above problem, a method known to a person of skill in the art is to add a DC-to-DC converter in the circuit or provide a reference voltage through the system, though both circuit structures thereof are complicated, which is of no avail for SoC implementation.